Hi all Would much appreciate a little help with a problem. In short, my executable is linked (implicitly) to a shared library X.so. X.so uses
dlopen(path.c_str(), RTLD_NOW | RTLD_DEEPBIND | RTLD_GLOBAL) to open Y.so, then dlsym() to obtain an exported C function from Y. The exported C function returns an object of class P, and calling a member function of P raises an exception. This exception leaves Y as a known type, and is caught as (...), i.e. unrecognised, in X. I think I understand the principles of this problem, but try as I might (and I have tried a lot), I just can't get an exception thrown in Y to be caught as the same type in X. I know this is sort of an FAQ, and I've read a few how-tos about it over the past couple of days, but I must still be doing something wrong. Perhaps someone can point out my silly mistake? The exception class (brahms::error::Error) is declared in error.h, and defined in error.cpp, which gets compiled into a X.so. I run: nm -C -D X.so | grep error | grep typeinfo and get... 000afb84 V typeinfo for brahms::error::Error 00096b5b V typeinfo name for brahms::error::Error I compile Y.so, which includes error.h, and run the same nm line on that to give 0002ae44 V typeinfo for brahms::error::Error 0002409d V typeinfo name for brahms::error::Error That is, the symbol brahms::error::Error typeinfo is "V" in both DSOs. also for "typeinfo name". I can't decode "typeinfo name", nor can I really say I understand the significance of "V", as it is described in man nm (it will defer to a "normally defined" symbol, but I can't find a definition of that, nor any indication of how to generate one for a typeinfo). My compile lines are: g++ -D_GNU_SOURCE -fPIC -Werror -Wall -ffast-math -pthread -O3 - fvisibility=hidden -fvisibility-inlines-hidden X.cpp -o X.so.0.7.3 g++ -D_GNU_SOURCE -fPIC -Werror -Wall -ffast-math -pthread -O3 - fvisibility=hidden -fvisibility-inlines-hidden -shared Y.cpp -o Y.so. 0.7.3 (some local information ellided). I am using the "hidden" flags on the advice of http://gcc.gnu.org/wiki/Visibility but I was having this problem before I tried that approach, so am confident it's unrelated. Since adding the hidden flags, my exception class is declared with an attribute, thus: struct __attribute__ ((visibility("default"))) Error { Error(); ... }; in both builds (i.e. there's no macro magic about that attribute, it's exactly as written above). Running the following: LD_DEBUG=files,symbols,bindings myapp > out 2>&1 generates an awful lot of data, of which i imagine the following is relevant: ... 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=brahms- execute [0] 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=/usr/lib/ libXt.so.6 [0] 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=/usr/lib/ libXaw.so.7 [0] 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=/lib/tls/ i686/cmov/librt.so.1 [0] 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=X.so [0] 27234: binding file X.so [0] to X.so [0]: normal symbol `_ZTSN6brahms5error5ErrorE' ... 27234: symbol=_ZTSN6brahms5error5ErrorE; lookup in file=/home/ user/SystemML/bin/Y.so [0] 27234: binding file /home/user/SystemML/bin/Y.so [0] to /home/ user/SystemML/bin/Y.so [0]: normal symbol `_ZTSN6brahms5error5ErrorE' ... I note there is a path on the second binding, not the first - relevant? I've no idea. In any case, it seems to agree with the uncaught exception problem: the symbol is bound to the one in X, from X, and to the one in Y, from Y. Whereas I think what I'm seeking is that the symbol in Y gets "bound" (in truth, I'm not 100% on exactly what that means) to the one in X, and thus they both agree on address- based typeinfo(). My hope is that I'm just passing a wrong flag to the compiler, or some such? Any help much appreciated :) Ben _______________________________________________ help-gplusplus mailing list help-gplusplus@gnu.org http://lists.gnu.org/mailman/listinfo/help-gplusplus
